Your think piece on “Policy frameworks for increasing soil fertility in Africa: debating the alternatives” is really interesting.
Certainly, in many situations external input of plant nutrients is needed to increase the yields and the soil fertility and this is well demonstrated by your list of “models”, where all, except the last one, explicitly aims at increasing the productivity through the increased use of chemical fertilizers.
There is however on large and free supply of plant nutrients available even to the most poor and which you do not mention, namely the plant nutrients in the human excreta. Due to the mass balance over the adult human body, the excreta contain all the macro nutrients and the micro nutrients in essentially the same proportions as supplied by the food (even though small amounts are lost with hair, nails, sweat, etc.). Calculations by Arno Rosemarin and Ian Caldwell in the SEI Report “Sustainable Pathways to Attain the Millennium Development Goals: Assessing the Key Role of Water, Energy and Sanitation” (Figure 4-21, relevant chapters attached) show that in the Sub-Saharan region the amounts nitrogen and phosphorus in the human excreta are of the same order as that used in 2002 in the form of chemical fertilizers. Yet, this option for providing locally available plant nutrients is not mentioned in your document.
As we see it, the excreta plant nutrients have several advantages:
- Available also to the most poor, at least in small amounts – from the own family
- No import and thus no impact on the trade balance
- Two complete and complementing fertilizers, urine and treated faeces (see the attached “Guidelines on use of urine and faeces in crop production”)
*Urine has the largest flows of nitrogen, phosphorus, potassium and sulphur, and after degradation of the urea nitrogen, essentially of of these nutrients are in the ionic form, i.e. they are easily available. The hygiene risk of non-contaminated urine is low.
*While the flow of macro nutrients in faeces is smaller, its flows of many micro nutrients are larger and it also provides valuable organic matter. However, the pathogen risk associated with faeces is large and they must always be handled, treated and reused in such a way that this reuse chain is considered safe, i.e. its risks are considered acceptable.
- The complementing types of the excreta fertilisers means that the fertilizing schemes can be optimized, e.g. using the urine mainly on nitrogen demanding crops i.e. maize and the faeces on e.g. legumes.
- A further advantage is that the plant nutrient factories consists of toilets, i.e. programs to increase the excreta plant nutrient availability to crop production simultaneously improves the sanitation situation and decreases the pollution and degradation of the environment (MDG no 7).
Sanitation systems aimed at reuse of the excreta plant nutrients are often called ecological sanitation (ecosan), but a very good term for this used by FAO and IFAD is productive sanitation.
We believe in great synergies, especially for small holder farmers in dry regions, when productive sanitation (better plant nutrient supply) is combined with rain water harvesting and water conserving practices and sustainable agricultural practices (improving the soil organics) and are organizing a seminar (attached) August 17th on this “triple green revolution” approach at the World Water Week in Stockholm. Together with IFAD and CREPA, which is experienced in ecological sanitation in West Africa, we are also staring a project on this triple green revolution approach.
Eco-Agriculture and Sanitation System Technology Expert
Stockholm Environment Institute